The present invention relates to a semiconductor device, and more specifically, it relates to a resin-sealed semiconductor device and a manufacturing method thereof.
With mobile apparatuses such as notebook computers having come to be used widely in recent years, resin-sealed semiconductor devices mounted in such apparatuses need to achieve a lower profile, further miniaturization and reduced weight. Accordingly, numerous resin-sealed semiconductor devices have been proposed in response to these technical requirements.
FIG. 4 illustrates an example of such a semiconductor device in the prior art. Wiring 104 constituted of copper (Cu) are electrically connected to electrode pads 102 formed at the primary surface of a semiconductor element 100. Cu posts 106 having a height of approximately 150 micrometer are connected with the wiring 104. Then, a resin layer 108 is formed at a height corresponding to the height of the Cu posts 106 for sealing. External connection terminals constituted of a metal such as solder balls 110 are formed at the tips of the Cu posts 106 that are exposed.
The process up to this point is implemented on a wafer with a plurality of semiconductor elements 100 arrayed thereon. Then, the wafer undergoes a dicing process to be divided into individual pieces. The resulting semiconductor devices are so-called chip-size package semiconductor devices whose size is very close to the size of the semiconductor elements.
During the process for manufacturing the device described above, a wafer comprising a plurality of semiconductor elements 100 is set at a mold die constituted of an upper die 112 and a lower die 114, as illustrated in FIG. 5, to achieve sealing with a resin so as to completely cover the Cu posts 106.
If foreign matter such as dirt is present inside the mold die at this time, the foreign matter may come into contact with the rear surfaces of the semiconductor elements 100 to scar them and even cause cracks 116.
In addition, surface polishing is performed by using an abrasive material 118, as illustrated in FIG. 6 to expose the tips of the Cu posts 106 after the resin curing process.
During the polishing process, the wafer is vacuum held through vacuum holes 122 formed at a polishing stage 120 to secure the wafer. However, if the wafer is warped, the vacuum hold may not be successful, which, in turn, may make it impossible to perform surface polishing.
Such warping of the wafer occurs due to the difference between the coefficient of expansion of the wafer (the semiconductor element 100) and the coefficient of expansion of the resin layer 108 sealed thereupon. Such warping occurs to varying degrees depending upon the thickness of the resin layer 5 and the type of material used to constitute the resin layer 5.
In addition, semiconductor devices achieved by forming a sealing resin layer at the rear surfaces of the semiconductor elements as well as at the primary surfaces have been proposed in recent years. However, there is a problem in that since the resin is injected at both surfaces, the total thickness of the resin layer increases.